Context
Galatians 1:8-9 should be read within the flow of its chapter and the larger argument of Galatians.
Common Interpretations
Twice. The same warning, repeated in consecutive verses. Paul does not say "be careful about alternate gospels." He says let them be accursed. The strength of that language tells you how high the stakes are. The gospel is not a starting point that can be refined or reframed or supplemented with better ideas. It is a fixed proclamation. Change it, and you have not improved it. You have lost it. The core is the core. Everything else is built on top of it — or it is built on sand.
Current Position
No defined position is stated here yet beyond the common interpretations above. As related study develops, this section will be updated where the text warrants a clearer conclusion.